This concept of the flap valve has been in existence in various forms of manufacture for about 500 years. Most of these types of valve are used to allow fluid or gas to move in one direction and stop back flow when pumping is stopped. The valve comprises a valve body having a duct passing through the body with a flap member mounted on the valve body so as to pivot from an open position allowing fluid to flow through the duct to a closed position resting against a seat in the duct and closing the duct to prevent back flow thorough the duct. The valve includes a sealing disc or plate within the valve body with a mounting arrangement which allows the plate to pivot between the open and closed positions. The mounting should have a form of universal joint allowing movement without hindering the sealing such that the disc is able to accommodate wear and or misalignment without failure or allowing seepage. In addition, the valve should be manufacture in a manner which is inexpensive and provides a construction which does not allow metal parts to enter the stream in the event of damage to the valve.
Therefore further improvements to provide enhanced operation and ease of manufacture are still possible.